阅读说明：本技术 一种高速电机驱动的离心式压缩机和鼓风机 (Centrifugal compressor and air blower driven by high-speed motor ) 是由 长谷川和三 鲁寅 于 2019-02-01 设计创作，主要内容包括：本发明涉及一种高速电机驱动的离心式压缩机和鼓风机。以往存在这样的问题：在离心式压缩机中,来自离心式压缩机的叶轮的背面的、100℃～170℃高温的泄漏压缩气体会对轴承进行加热,以至超过轴承的耐热温度。为此,以往采用使轴承远离叶轮的方案。结果,导致产生转子整体变长,转子的临界转速下降,转子无法高速运转,无法获得充分的输出压力。为了解决上述问题,本发明采用了如下方案：设置翼片结构,由翼片结构进行送气,使气体在轴封处的流动逆流。由此,防止自轴封的泄漏,防止由泄漏气体对轴承进行加热。最终达到了如下效果：转子的长度变短,提高了临界速度,提高了运转转速,从而使运转压力上升,能够获得充分的输出压力。(The present invention relates to a high speed motor driven centrifugal compressor and blower. The prior art has the following problems: in a centrifugal compressor, a bearing is heated by a high-temperature 100-170 ℃ leaked compressed gas from the back surface of an impeller of the centrifugal compressor to exceed the heat-resistant temperature of the bearing. For this reason, conventionally, a bearing is spaced apart from the impeller. As a result, the rotor as a whole becomes longer, the critical rotational speed of the rotor decreases, the rotor cannot be operated at high speed, and sufficient output pressure cannot be obtained. In order to solve the problems, the invention adopts the following scheme: the fin structure is arranged to feed gas to the shaft seal so that the gas flows in a reverse direction. Thereby, leakage from the shaft seal is prevented, and heating of the bearing by the leakage gas is prevented. The following effects are finally achieved: the length of the rotor is shortened, the critical speed is increased, the operation pressure is increased, and sufficient output pressure can be obtained.)

1. A centrifugal compressor driven by a high-speed motor is characterized in that,

the centrifugal compressor includes the following configuration: the centrifugal compressor is provided with a fin structure for feeding gas, the fin structure makes the leakage gas leaked from the back of the impeller flow back to the gas inlet side of the gas passage to prevent the leakage gas from leaking from the gap between the shaft seal and the transmission shaft,

the gas passage is provided in a rear housing of the centrifugal compressor, and discharges the leakage gas from a rear surface of the impeller and the gas from the vane structure.

2. A blower driven by a high-speed motor is characterized in that,

the blower includes the following construction: the blower is provided with a fin structure for feeding air, the fin structure makes the leakage gas leaked from the back of the impeller flow back to the air inlet side of the air passage to prevent the leakage gas from leaking from the gap between the shaft seal and the transmission shaft,

the gas passage is provided in a rear housing of the blower, and discharges the leakage gas from a rear surface of the impeller and the gas from the vane structure.

3. A high speed motor driven centrifugal compressor according to claim 1 or a high speed motor driven blower according to claim 2,

the centrifugal compressor comprises a back shell, the transmission shaft penetrating through the back shell, the shaft seal arranged between the back shell and the transmission shaft, the impeller arranged at one end of the transmission shaft, and a bearing arranged at the other end side of the transmission shaft,

the back housing has a first wall surface facing a back surface of the impeller, a gap being provided between the first wall surface and the back surface of the impeller,

a gas passage is opened in the rear surface case, and the gas passage penetrates the rear surface case from the first wall surface.

4. A high speed motor driven centrifugal compressor or a high speed motor driven blower according to claim 3,

the fin structure is arranged on the part, located on the back face of the impeller, of the transmission shaft and is installed on the part, located between the back face of the impeller and the shaft seal, of the transmission shaft, the fin structure is provided with a suction end located on the side of the shaft seal and a discharge end located on the side of the impeller, and when the fin structure rotates, gas at the suction end is guided to the discharge end and is output towards the gap.

5. A high speed motor driven centrifugal compressor or a high speed motor driven blower according to claim 4,

the fin structure comprises a mounting disc and fins, the mounting disc is fixedly mounted on the transmission shaft, and the fins are fixedly mounted on the mounting disc.

6. A high speed motor driven centrifugal compressor or a high speed motor driven blower according to claim 5,

the fin has a plurality of, and a plurality of the fin is evenly distributed along the circumference of the mounting disc.

7. A high speed motor driven centrifugal compressor or a high speed motor driven blower according to claim 3,

the wing structure is arranged on the back face of the impeller, is positioned on the back face of the impeller and is closer to the transmission shaft than the air inlet of the air passage, the wing structure is provided with an air suction end positioned on the side of the transmission shaft and an air exhaust end positioned on the side of the air inlet, and when the wing structure rotates, the air at the air suction end is guided to the air exhaust end and is output towards the air inlet.

8. A high speed motor driven centrifugal compressor or a high speed motor driven blower according to claim 7,

the wing structure comprises a mounting disc and wings, the mounting disc is fixedly mounted on the back of the impeller, and the wings are fixedly mounted on the mounting disc.

9. A high speed motor driven centrifugal compressor or a high speed motor driven blower according to claim 8,

the fin has a plurality of, and a plurality of the fin is evenly distributed along the circumference of the mounting disc.

10. A high speed motor driven centrifugal compressor or a high speed motor driven blower according to claim 7,

the vane structure includes a vane formed integrally with the impeller.

11. A high speed motor driven centrifugal compressor or a high speed motor driven blower according to claim 10,

the vanes are distributed evenly along the circumference of the impeller.

12. A high speed motor driven centrifugal compressor or a high speed motor driven blower according to claim 3,

the wing structure is arranged on the part of the transmission shaft opposite to the shaft seal, the wing structure comprises a wing, the wing is integrated with the transmission shaft, the wing structure is provided with a suction end positioned on the bearing side and a discharge end positioned on the impeller side, and when the wing structure rotates, gas at the suction end is guided to the discharge end and is output towards the gap.

13. A high speed motor driven centrifugal compressor or a high speed motor driven blower according to claim 12,

the fin has a plurality of, and a plurality of the fin is along the even distribution of transmission shaft circumference.

14. A high speed motor driven centrifugal compressor or a high speed motor driven blower according to claim 3,

the gas passage includes the gas inlet, a gas outlet, and a gas passage that communicates the gas inlet with the gas outlet, the gas inlet is located at a position radially close to the axis of the transmission shaft, and the gas outlet is located at a position radially distant from the axis of the transmission shaft.

15. A high speed motor driven centrifugal compressor or a high speed motor driven blower according to claim 14,

the back shell is provided with a second wall surface facing the side where the bearing is located, the air inlet is formed in the first wall surface, and the air outlet is formed in the second wall surface.

16. A high speed motor driven centrifugal compressor according to claim 1 or a high speed motor driven blower according to claim 2,

the gas passage is provided in plurality, and the plurality of gas passages are provided at the same interval in the circumferential direction.

17. A high speed motor driven centrifugal compressor or a high speed motor driven blower according to claim 3,

the first wall surface is provided with an end face seal.

18. A high speed motor driven centrifugal compressor or a high speed motor driven blower according to claim 3,

the high-speed motor comprises a stator and a rotor, the rotor is fixedly installed on the transmission shaft, the stator is arranged around the rotor, and the bearing is located between the rotor and the shaft seal.

Technical Field

The present invention relates to a centrifugal compressor and blower driven by a high speed motor.

Background

The centrifugal compressor is used as a power source and an air source in a manufacturing plant. In order to increase the rotational speed of the impeller of the centrifugal compressor, a gear speed increasing machine has been used. In recent years, high-speed motors have appeared, and direct-drive centrifugal compressors (blowers) have been developed.

Fig. 1 shows a structure of a centrifugal compressor directly driven using a high-speed motor in the related art. As shown in fig. 1, the centrifugal compressor includes a drive shaft 1, an impeller 2, a scroll 3, a diffuser 4, a back surface housing 5, a shaft seal 6, a bearing 7, a stator 8, and a rotor 9. The transmission shaft 1 penetrates a through hole provided in the rear housing 5, and a shaft seal 6 such as a labyrinth shaft seal is provided between the transmission shaft 1 and the rear housing 5. The impeller 2 is fixedly disposed at one end of the transmission shaft 1 penetrating the rear housing 5, and a gap is provided between the impeller 2 and the rear housing 5 to allow the impeller 2 to rotate. A rotor 9 fixed to the drive shaft 1 is provided on the other end side of the drive shaft 1, and a stator 8 is provided around the rotor 9 with a space therebetween. Further, a bearing 7 such as an air bearing or a magnetic bearing is provided between the shaft seal 6 and the rotor 9 in the propeller shaft 1. The scroll 3 is fixedly connected to the rear housing 5 at one end side of the transmission shaft 1, and a diffuser 4 is provided inside the scroll 3.

When the centrifugal compressor works, the rotor 9 rotates at a high speed, the transmission shaft 1 drives the impeller 2 to rotate at a high speed, and the impeller 2 sucks low-temperature and low-pressure gas and conveys high-temperature and high-pressure gas towards the diffuser 4.

In such a centrifugal compressor directly driven by a high-speed motor, there are the following problems. Since a gap exists between the impeller 2 and the back casing 5, as shown by the arrow in fig. 1, a part of the high-temperature and high-pressure gas (100 to 170 ℃) enters the gap in the arrow direction. Further, since the labyrinth shaft seal 6 and the transmission shaft 1 are not completely sealed, the above-mentioned part of the high-temperature and high-pressure gas continues to leak toward the bearing 7 through the gap between the shaft seal 6 and the transmission shaft 1.

The high-temperature (100 to 170 ℃) leaked compressed gas from the back surface of the impeller of the centrifugal compressor heats the air bearing and the magnetic bearing to exceed the heat-resistant temperature of the bearing. Typically, in a 7Bar centrifugal compressor, about 1% of the high temperature leakage gas is discharged from the impeller of the high pressure section centrifugal compressor.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a centrifugal compressor capable of greatly reducing the amount of leakage of high-temperature gas that leaks through a gap between a shaft seal and a drive shaft.

Therefore, the invention provides the following technical scheme.

A first aspect of the present invention is a centrifugal compressor driven by a high-speed motor, characterized by comprising: the centrifugal compressor is provided with a fin structure for feeding gas, which prevents leakage gas leaking from a gap between a shaft seal and a drive shaft by causing the leakage gas leaking from the back surface of an impeller to flow backward toward the gas inlet side of a gas passage provided in a back housing of the centrifugal compressor, and which discharges the leakage gas from the back surface of the impeller and the gas from the fin structure.

A second aspect of the present invention is a blower driven by a high-speed motor, characterized by comprising: the blower is provided with a fin structure for feeding gas, which prevents leakage gas leaking from a gap between a shaft seal and a transmission shaft by causing the leakage gas leaking from the back surface of an impeller to flow backward toward the gas inlet side of a gas passage provided in a back housing of the blower, and which discharges the leakage gas from the back surface of the impeller and the gas from the fin structure.

A third aspect of the present invention is a high-speed motor-driven centrifugal compressor according to the first aspect or a high-speed motor-driven blower according to the second aspect, characterized in that the centrifugal compressor includes a back casing, the transmission shaft penetrating the back casing, the shaft seal provided between the back casing and the transmission shaft, the impeller provided at one end of the transmission shaft, and a bearing provided at the other end side of the transmission shaft, the back casing has a first wall surface facing a back surface of the impeller, a gap is provided between the first wall surface and the back surface of the impeller, and a gas passage is provided in the back casing, the gas passage penetrating the back casing from the first wall surface.

A fourth technical means is the centrifugal compressor or the blower driven by the high-speed motor according to the third technical means, wherein the fin structure is provided at a portion of the drive shaft located on a back surface of the impeller, and is attached to a portion of the drive shaft located between the back surface of the impeller and the shaft seal, the fin structure has a suction end located on a side of the shaft seal and a discharge end located on a side of the impeller, and the fin structure guides gas at the suction end to the discharge end and outputs the gas toward the gap when rotating.

A fifth technical means is the high-speed motor-driven centrifugal compressor or the high-speed motor-driven blower according to the fourth technical means, wherein the fin structure includes a mounting plate and a fin, the mounting plate is fixedly attached to the drive shaft, and the fin is fixedly attached to the mounting plate.

A sixth aspect of the present invention is the high-speed motor-driven centrifugal compressor or the high-speed motor-driven blower according to the fifth aspect, wherein the number of the fins is plural, and the plural fins are uniformly distributed along a circumferential direction of the mounting plate.

A seventh aspect of the present invention is the high-speed motor-driven centrifugal compressor or the high-speed motor-driven blower according to the third aspect, wherein the fin structure is provided on a back surface of the impeller, and is located on a portion of the back surface of the impeller that is closer to the drive shaft than the air inlet of the gas passage, the fin structure has an air intake end located on the drive shaft side and an air exhaust end located on the air inlet side, and the fin structure guides gas at the air intake end to the air exhaust end and outputs the gas toward the air inlet when rotating.

An eighth technical means is the high-speed motor-driven centrifugal compressor or the high-speed motor-driven blower according to the seventh technical means, wherein the vane structure includes a mounting plate fixedly attached to a back surface of the impeller and a vane fixedly attached to the mounting plate.

A ninth aspect of the present invention is the high-speed motor-driven centrifugal compressor or the high-speed motor-driven blower according to the eighth aspect, wherein the number of the fins is plural, and the plural fins are uniformly distributed along a circumferential direction of the mounting plate.

A tenth technical means is the high-speed motor-driven centrifugal compressor or the high-speed motor-driven blower according to the seventh technical means, wherein the vane structure includes a vane formed integrally with the impeller.

An eleventh aspect of the present invention is the high-speed motor-driven centrifugal compressor or the high-speed motor-driven blower according to the tenth aspect, wherein the plurality of vanes are uniformly distributed along a circumferential direction of the impeller.

A twelfth technical means of the present invention is the high-speed motor-driven centrifugal compressor or the high-speed motor-driven blower according to the third technical means, wherein the fin structure is provided at a portion of the drive shaft opposite to the shaft seal, the fin structure includes a fin formed integrally with the drive shaft, the fin structure has a suction end on the bearing side and a discharge end on the impeller side, and the fin structure guides gas at the suction end to the discharge end and outputs the gas toward the gap when rotating.

A thirteenth aspect of the present invention is the high-speed motor-driven centrifugal compressor or the high-speed motor-driven blower according to the twelfth aspect, wherein the number of the fins is plural, and the plural fins are uniformly distributed along the circumferential direction of the drive shaft.

A fourteenth technical means is the high-speed motor-driven centrifugal compressor or the high-speed motor-driven blower according to the third technical means, wherein the gas passage includes the gas inlet, a gas outlet, and a gas passage that communicates the gas inlet and the gas outlet, the gas inlet is located at a position radially close to an axis of the drive shaft, and the gas outlet is located at a position radially distant from the axis of the drive shaft.

A fifteenth technical means is the high-speed motor-driven centrifugal compressor or the high-speed motor-driven blower according to the fourteenth technical means, wherein the rear housing has a second wall surface facing the side where the bearing is located, the air inlet is opened in the first wall surface, and the air outlet is opened in the second wall surface.

A sixteenth technical means is the high-speed motor-driven centrifugal compressor according to the first technical means or the high-speed motor-driven blower according to the second technical means, wherein the plurality of gas passages are provided at equal intervals in a circumferential direction.

A seventeenth technical means is the high-speed motor-driven centrifugal compressor or the high-speed motor-driven blower according to the third technical means, wherein the first wall surface is provided with an end face seal.

An eighteenth technical means of the present invention is the centrifugal compressor driven by the high-speed motor according to the first technical means or the blower driven by the high-speed motor according to the second technical means, further comprising a high-speed motor, wherein the high-speed motor comprises a stator and a rotor, the rotor is fixedly mounted on the transmission shaft, the stator is disposed around the rotor, and the bearing is located between the rotor and the shaft seal.

By adopting the above technical solution, the present invention provides a centrifugal compressor and a blower driven by a high-speed motor, which can prevent heating of a bearing by changing the flow direction of leakage gas from a shaft seal to be toward an impeller side, thereby shortening the length of the entire rotor, increasing the critical rotation speed of the rotor, increasing the operating rotation speed, and obtaining a sufficient output pressure. Further, since the cooling gas of the rotor can be reduced, the overall efficiency can be improved.

Drawings

Fig. 1 shows a block diagram of a centrifugal compressor in the prior art.

Fig. 2 shows a structural view of a centrifugal compressor according to a first embodiment of the present invention.

Fig. 3 shows an enlarged view of a portion a in fig. 2.

A top view of the first embodiment of the fin structure is shown in fig. 4.

Fig. 5 shows a structure of a centrifugal compressor according to a second embodiment of the present invention.

A top view of the second embodiment of the fin structure is shown in fig. 6.

Fig. 7 shows a structure of a centrifugal compressor according to a third embodiment of the present invention.

A top view of the third embodiment of the fin structure is shown in fig. 8.

Description of the reference numerals

1, a transmission shaft; 2, an impeller; 21 a back surface; 3, a volute; 31 an air suction port; a 32 diffusion flow path; 33 a vortex flow path; 4 a diffuser; 5 a back shell; 51 a first wall surface; 52 a second wall; 53 through holes; 54 gas passages; 541 an air inlet; 542 air outlet; 543 a gas passage; a 55 face seal; 6, shaft sealing; 61 flange part; 7, a bearing; 8, a stator; 9 a rotor; 10. 10', 10 "fin structures; 101. 101' mounting a disc; 102. 102', 102 "flap.

Detailed Description

Exemplary embodiments of a centrifugal compressor of the present invention are described below with reference to the accompanying drawings. It should be understood that the detailed description is only intended to teach one skilled in the art how to practice the invention, and is not intended to be exhaustive or to limit the scope of the invention.

In the present invention, the term "radial direction" refers to the direction of the diameter of the drive shaft, the term "axial direction" refers to the direction of the central axis of the drive shaft, the term "circumferential direction" refers to the direction around the central axis of the drive shaft, and the term "back surface of the impeller" refers to the surface of the impeller opposite to the back surface housing.

First embodiment

A first embodiment of the invention will now be described with reference to figures 2 to 4.

Fig. 2 shows a configuration diagram of a centrifugal compressor according to a first embodiment of the present invention, fig. 3 shows an enlarged view of a portion a in fig. 2, and fig. 4 shows a plan view of a vane structure of the first embodiment.

As shown in fig. 2 and 3, the present invention provides a centrifugal compressor, which includes a drive shaft 1, an impeller 2, a scroll 3, a diffuser 4, a back housing 5, a shaft seal 6, a bearing 7, a vane structure 10, and a high-speed motor.

The propeller shaft 1 is inserted through a through hole 53 formed in the center of the rear case 5, and a shaft seal 6 such as a labyrinth shaft seal is provided between the propeller shaft 1 and the rear case 5. The other end of the shaft seal 6 has a flange portion 61 projecting radially outward over the entire circumference. When the shaft seal 6 is disposed between the propeller shaft 1 and the rear housing 5, the flange portion 61 abuts against the rear surface of the rear housing 5. In addition, as for the specific structure of the labyrinth shaft seal, a design conventional in the art may be employed, and a description thereof will be omitted. The shaft seal 6 may also be a dry gas seal or a carbon ring seal.

The impeller 2 is fixedly disposed at one end of the transmission shaft 1 penetrating the rear housing 5, and a gap is provided between the rear surface of the impeller 2 and the rear housing 5 to allow the impeller 2 to rotate. Specifically, one end of the drive shaft 1 penetrates a first center hole provided in the center of the impeller 2, and is screwed from one end of the drive shaft 1 by a locknut, whereby the impeller 2 is fixedly provided at one end of the drive shaft 1. The back of the impeller 2 is circular.

Preferably, the first wall surface 51 is provided with a face seal 55, the face seal 55 being arranged opposite to an end of the impeller 2 radially remote from the drive shaft 1. Wherein the face seal 55 is annular. Thus, the face seal 55 can reduce the amount of high-temperature and high-pressure gas entering the above-described gap. Preferably, the face seal 55 is a labyrinth seal. Furthermore, the face seal may also be a dry gas seal or a carbon ring seal.

A fin structure 10 is provided in a space between the back face 21 of the impeller 2 and the other end face of the shaft seal 6 in the through hole 53. Details of the airfoil structure 10 will be described later.

The high-speed motor comprises a stator 8 and a rotor 9, the stator 8 and the rotor 9 are arranged around the rotor 9 at intervals, and the rotor 9 is fixedly arranged at the other end side of the transmission shaft 1 opposite to the side where the impeller 2 is arranged. The high speed motor causes the drive shaft 1 to rotate about the central axis of the drive shaft 1 by the interaction between the stator 8 and the rotor 9.

Further, a bearing 7 is provided between the shaft seal 6 and the rotor 9 on the propeller shaft 1. Preferably, the bearing 7 is an air bearing or a magnetic bearing.

The scroll 3 is fixed to the back casing 5 around the impeller 2, the scroll 3 includes a suction port 31 and a scroll flow path 33, and a diffusion flow path 32 is formed between the scroll 3 and the back casing 5. The suction port 31 and the diffuser flow path 32 communicate with each other through a gap between the impeller 2 and the scroll 3, and the diffuser flow path 32 communicates with the scroll flow path 33. The diffuser 4 is fixedly provided in the scroll 3 and located in the diffuser flow path 32 to decelerate the gas.

Next, the structure of the flap structure 10 and the rear surface case 5 will be described in detail.

As mentioned before, the fin structure 10 is located in the space between the back face 21 of the impeller 2 and the other end face of the shaft seal 6 in the through hole 53, the fin structure 10 comprising the mounting plate 101 and the fins 102.

The mounting plate 1 is in the shape of a curved truncated cone, and the outer wall surface of the mounting plate 1 is formed as a curved surface recessed toward the center line of the mounting plate 1.

The fins 102 are fixedly provided on the outer wall surface of the mounting plate 101. Preferably, the plurality of fins 102 is uniformly distributed along the circumferential direction of the mounting plate 101 as shown in fig. 4.

The fin structure 10 is disposed between the impeller 2 and the shaft seal 6, almost accommodated in the through hole 53 of the back housing 5. This makes it possible to make the centrifugal compressor compact. The mounting plate 101 is fixed to the back surface 21 of the impeller 2. The mounting disc 101 is provided with a second central hole, the central axis of the second central hole is collinear with the central axis of the first central hole of the impeller 2, and the mounting disc 101 is sleeved on the transmission shaft 1 through the second central hole. In this way, the fin structure 10 and the impeller 2 can simultaneously rotate synchronously about the central axis of the drive shaft 1 with the rotation of the drive shaft 1.

The fins 102 are configured to extend closer to the drive shaft 1 as they approach the shaft seal 6, with the end of the fins 102 that is closer to the shaft seal 6 being the suction end and the end that is away from the shaft seal 6 being the discharge end. The vanes 102, when rotated, are capable of directing the gas at the suction end to the discharge end and out toward the gap as described above. In this way, the movement direction of the gas output from the exhaust ends of the fins 102 is opposite to the flow direction of the high-temperature and high-pressure gas in the gap, and the high-temperature and high-pressure gas can be effectively prevented from flowing toward the shaft seal 6 and leaking toward the bearing 7 through the gap between the shaft seal 6 and the transmission shaft 1.

The rear housing 5 has a first wall surface 51 and a second wall surface 52, the first wall surface 51 being opposed to the rear surface 21 of the impeller 2, and the second wall surface 52 facing the bearing 7. Between the first wall surface 51 and the second wall surface 52, a gas passage 54 and a through hole 53 are opened. The gas passage 54 penetrates the rear surface case 5, as will be described later in detail. The through hole 53 is located at a substantially central portion of the rear case 5, through which the transmission shaft 1 passes.

The gas passage 54 includes a gas inlet 541 opening to the first wall 51, a gas outlet 542 opening to the second wall 52, and a gas passage 543 between the gas inlet 541 and the gas outlet 542. The gas passage 543 communicates the gas inlet 541 and the gas outlet 542 with each other inside the rear case 5. The air inlet 541 is provided at a portion close to the axis in the radial direction, and the air outlet 542 is provided at a portion away from the center of the axis in the radial direction and located radially outside the bearing. Thereby, the air outlet 542 is distanced from the bearing 7 in the radial direction.

In the present embodiment, the gas passage 543 preferably extends in a step shape, and in detail, extends from the gas inlet 541 toward the axial direction, then extends in a radial direction perpendicular to the axial direction inside the back housing 5, and then extends in the axial direction toward the gas outlet 542. When the gas passage 543 is formed in a stepped shape, the flow resistance of the gas passage 543 can be increased, and thus a large amount of gas sucked into the gap between the impeller 2 and the scroll 3 can be prevented from leaking from the gas passage 543. However, the gas passage 543 may directly connect the gas inlet 541 and the gas outlet 542 in an inclined manner, as long as the high-temperature and high-pressure gas can be guided from the gas inlet 541 to the gas outlet 542.

Preferably, there are a plurality of the gas passages 54, and the plurality of gas passages 54 are provided in the rear surface case 5 at substantially the same intervals in the circumferential direction. Preferably, the cross-sections of the gas inlet 541, the gas outlet 542, and the gas passage 543 are all circular in shape. Preferably, the air outlet 542 is provided at a position as far as possible from the axial center in the radial direction so as to be as far as possible from the bearing 7.

When the centrifugal compressor is operated, the impeller 2 sucks gas from the inlet 31, discharges the gas to the diffuser flow path 32, and the gas whose pressure has been increased by the diffuser flow path 32 enters the scroll flow path 33. Some of the gas discharged from the impeller 2 enters the gap between the back surface 21 of the impeller 2 and the first wall surface 51.

The gas flow direction in the a-section structure in the operation of the centrifugal compressor of the present invention will be briefly described with reference to the arrows in fig. 3.

As shown in fig. 3, when the centrifugal compressor is operated, the high-speed motor drives the transmission shaft 1 to rotate at a high speed, and further drives the impeller 2 and the vane structure 10 to rotate at a high speed. Some of the high-temperature and high-pressure gas discharged from the impeller 2 rotating at a high speed enters a gap between the back surface 21 of the impeller 2 and the first wall surface 51 via the end face seal 55. The high speed rotating airfoil structure 10 directs the gas at its suction end to its discharge end and discharges toward the gap. Since the gas pressure of the gas in the gap is higher than the gas pressure of the gas on the second wall surface 52 side of the rear surface case 5, the two flows of gas entering the gap are collected at the gas inlet 541 of the gas passage 54, enter the gas passage 543 through the gas inlet 541, and are finally discharged from the gas outlet 542. Wherein, as the gas at the suction end of the vane structure 10 is guided to the exhaust end, a negative pressure area is formed at the suction end of the vane structure 10, so that the gas at the side of the rotor 9 of the shaft seal 6 flows towards the suction end of the vane structure 10.

As mentioned above, a smaller fin structure 10 is provided between the back of the impeller 2 and the shaft seal 6. During rotation of the impeller 2, the gas is caused to flow in a direction (radial direction) opposite to the flow direction of the leakage gas leaking from the back surface of the impeller 2, thereby preventing the flow of the leakage gas leaking from the back surface of the impeller 2. In the case where the fin structure 10 is not present, the flow through the shaft seal 6 flows in the direction of the high-speed motor, but the provision of the fin structure 10 enables the gas to flow in the direction of the impeller 2. In order to suppress the flow of leakage gas from the back surface of the impeller 2 as much as possible, an end face seal 55 having a labyrinth seal structure is provided in the back casing 5.

The leakage gas that has passed through the end face seal 55 and the gas that has passed through the fin structure 10 merge and are discharged to the outside air through the gas passage 54 in the rear surface case 5. Thus, by changing the flow direction of the leakage gas from the shaft seal 6 toward the impeller side, heating of the bearing can be prevented, whereby the length of the entire rotor can be shortened, the critical rotation speed of the rotor can be increased, the operating rotation speed can be increased, and a sufficient output pressure can be obtained. Further, since the cooling gas of the rotor can be reduced, the overall efficiency can be improved.

Second embodiment

A second embodiment of the invention will now be described with reference to figures 5 to 6.

Fig. 5 shows a structure of a centrifugal compressor according to a second embodiment of the present invention. A top view of the second embodiment of the fin structure is shown in fig. 6.

In the second embodiment of the present invention, the same as the first embodiment is made except for the location where the fin structure 10' is provided and the shape and size thereof are adjusted to suit the location. The same portions as those in the first embodiment are denoted by the same reference numerals.

In the second embodiment, the fin structure 10' is provided on the surface of the impeller 2 opposite to the first wall surface 51. The fin structure 10 ' includes a mounting plate 101 ' and a fin 102 '. The center of the mounting plate 101 ' has a through hole 103 ', and the transmission shaft 1 penetrates the through hole 103 '. The mounting plate 101 ' is mounted to the surface of the impeller 2 opposite to the first wall surface 51, and the fins 102 ' are evenly arranged on the mounting plate 101 ' in the circumferential direction. In this way, the fin structure 10' and the impeller 2 can simultaneously rotate synchronously about the central axis of the drive shaft 1 with the rotation of the drive shaft 1.

The end of the wing 102' close to the transmission shaft 1 is a suction end, and the end close to the air inlet 541 is an exhaust end. The vanes 102' are capable of directing gas at the suction end to the discharge end as they rotate and out toward the inlet 541. In this way, the movement direction of the gas output from the exhaust ends of the fins 102' is opposite to the flow direction of the high-temperature and high-pressure gas in the gap, and the high-temperature and high-pressure gas can be effectively prevented from flowing toward the shaft seal 6 and leaking toward the bearing 7 through the gap between the shaft seal 6 and the transmission shaft 1.

Further, as a modification of the second embodiment, the fin 102 'may be directly integrated with the back surface of the impeller 2 without the aid of the mounting plate 101'. In this case, the fins 102 'may be machined by directly cutting the back surface of the impeller 2, or the fins 102' may be fixed to the back surface of the impeller 2 by welding or the like.

Third embodiment

A third embodiment of the present invention will be described with reference to fig. 7 to 8.

Fig. 7 shows a structure of a centrifugal compressor according to a third embodiment of the present invention, and fig. 8 shows a plan view of a vane structure of the third embodiment.

The third embodiment of the present invention is the same as the first embodiment except for the installation location and shape of the vane structure 10 "and the shaft seal 6". The same portions as those in the first embodiment are denoted by the same reference numerals.

In the third embodiment, the shaft seal 6 ″ may be configured to close most of the gap between the rear surface case 5 and the propeller shaft 1, and a larger gap is provided between the shaft seal 6 ″ and the propeller shaft 1 than in the first and second embodiments. The fin structure 10 "is provided at a portion of the drive shaft 1 opposite the shaft seal 6". The wing structure 10 "comprises wings 102", the wings 102 "being evenly distributed along the circumference of the propeller shaft 1. The fins 102 "may be obtained by cutting the propeller shaft directly, or the fins 102" may be fixed to the propeller shaft 1 by welding or the like. That is, in the third embodiment, the fin 102 ″ is formed integrally with the propeller shaft 1. In this way, the fin structures 10 "can simultaneously rotate synchronously with the rotation of the propeller shaft 1 about the central axis of the propeller shaft 1.

The end of the vane 102 "close to the bearing 7 is the suction end and the end facing away from the bearing 7 is the discharge end. The vanes 102 "are capable of directing gas at the suction end to the discharge end as it rotates and out toward the inlet 541. In this way, the movement direction of the gas output from the exhaust ends of the fins 102 "is opposite to the flow direction of the high-temperature and high-pressure gas in the gap, and the high-temperature and high-pressure gas can be effectively prevented from flowing toward the shaft seal 6" and leaking toward the bearing 7 through the gap between the shaft seal 6 "and the transmission shaft 1.

By adopting the technical scheme, the centrifugal compressor has at least one of the following advantages:

(1) in the centrifugal compressor of the invention, the fin structure is arranged on the part of the transmission shaft positioned on the back surface of the impeller or on the back surface of the impeller, so that high-temperature and high-pressure gas in a gap between the back surface of the impeller and the first wall surface of the back surface shell can be effectively prevented from further leaking through a gap between the shaft seal and the transmission shaft, and further, the adverse effect caused by heating the air bearing can be avoided.

(2) In the centrifugal compressor, the gas passage is arranged in the back shell, and the gas passage can guide the high-temperature and high-pressure gas in the gap between the back surface of the impeller and the first wall surface of the back shell to the side, opposite to the impeller, of the back shell, so that the leakage amount of the high-temperature and high-pressure gas in the gap towards the air bearing through the gap between the shaft seal and the transmission shaft is further reduced, and the adverse effect caused by too high gas pressure in the gap is also prevented.

(3) In the centrifugal compressor, the leakage amount of high-temperature and high-pressure gas in the gap leaking towards the air bearing through the gap between the shaft seal and the transmission shaft is greatly reduced, so that the air bearing can be arranged close to the shaft seal, and the gap for discharging the high-temperature and high-pressure gas is not required to be reserved between the shaft seal and the air bearing. Accordingly, the length of the transmission shaft can be shortened, the critical rotating speed which can be borne by the rotor is increased, and the rotor can drive the impeller to run at a high speed so as to obtain sufficient output pressure.

(4) In the centrifugal compressor of the invention, the end face sealing piece is arranged on the first wall face and is positioned at one end of the first wall face far away from the transmission shaft in the radial direction, so that the quantity of high-temperature and high-pressure gas entering the gap can be reduced, namely, the leakage quantity of the high-temperature and high-pressure gas in the gap leaking towards the air bearing through the gap between the shaft seal and the transmission shaft can be further reduced.

(5) Since the cooling gas of the rotor can be reduced, the overall efficiency can be improved.

The above embodiments describe the technical solution of the present invention in detail, but it should be added that:

1. although it is described in the above embodiment that the vane structure is fixed to the impeller, the present invention is not limited thereto, and the vane structure may be fixed to the drive shaft, and "fixing" referred to in the present invention includes fixing in an integrally formed form.

2. Although the gas outlet of the gas passage is opened to the second wall surface of the rear housing in the above embodiment, the present invention is not limited to this, and the gas outlet may be opened to a side wall surface of the rear housing perpendicular to the second wall surface as long as the high-temperature and high-pressure gas in the gap can be guided to the gas outside the centrifugal compressor.

3. Although it is described in the above embodiment that the cross-sectional shape of the gas passage is circular, the present invention is not limited thereto, and the cross-sectional shape of the gas passage may be polygonal or other irregular shapes, and the size of the cross-sectional shape of the gas passage may be equal everywhere or may be different.

4. Although the above description has been given by taking a centrifugal compressor as an example, the present invention is also applicable to a case where it is necessary to reduce the amount of axial leakage of gas, including a blower and the like.

5. In the above-described embodiment, the example in which the centrifugal compression mechanism is provided on one side of the transmission shaft of the high-speed motor has been described, but the present invention is not limited to this, and the centrifugal compression mechanism may be provided on both sides of the transmission shaft of the high-speed motor.

In addition, the scope of the present invention is not limited to the specific examples in the above-described embodiments, but falls within the scope of the present invention as long as a combination of technical features in the claims of the present invention is satisfied.